Technical Abstract:
Passage of cucumber (Cucumis sativus) through cell cultures produces plants with a distinctive mosaic (MSC) phenotype that shows paternal transmission. The mitochondrial (mt) DNA of cucumber is paternally transmitted and the MSC phenotype is associated with rearrangements in the mt DNA. We identified a unique nuclear locus (Psm for Paternal Sorting of Mitochondria) that controls sorting of paternally transmitted mitochondria. When a female plant homozygous for the Psm+ allele is crossed with MSC as the male, progenies show the MSC phenotype due to paternal transmission of the cucumber mt DNA. When the female plant is homozygous for the Psm- allele, almost all progenies from crosses with MSC plants are wild-type. Heterozygous female plants crossed with MSC males yield 1:1 MSC:WT progenies. The Psm-allele conditions sorting for relatively rare wild-type sublimons in the mt DNA of MSC plants. Towards the eventual cloning of this unique locus, we are exploiting synteny between cucumber and melon (Cucumis melo) to find markers tightly linked to Psm. An RFLP identified by probe CsP483 is linked at 10 cM to Psm and placed this locus on linkage group R of cucumber. CsP483 was mapped in melon to the end of linkage group 10. We mapped melon markers that flank CsP483 to reveal their orientation and position in cucumber relative to Psm.